Five ways laptops and tablets are getting better battery life

March 15, 2016 // By EDN Europe
by Faisal Ahmad - Director of Marketing, Power Management at Dialog Semiconductor
Although battery technology is developing far less rapidly than processor technology, laptops and tablets are achieving longer times away from the wall socket.

This is thanks to a combination of design techniques that aim to eke the most out of every milli-Ampere-hour that the battery can hold. Here are six key approaches manufacturers are using:

1) More energy

This is simple: just add more battery where you have the space. Integration and the move towards solid-state storage has compressed much of the electronics needed even for an advanced laptop computer down into a small number of integrated circuits (IC), resulting in a smaller motherboard. The space no longer needed for a standard-sized hard drive can be put to use by packing in another battery cell.

Convertibles put batteries into both the keyboard and tablet modules, often spread through the design to fit around motherboards and display cards. The downside of this approach is that it means the battery cannot easily be replaced. But the increased capacity working in tandem with power-saving techniques can deliver a full working day of energy for a typical user and still have some left charge over at the end.

2) The FinFET arrives

The technology inside laptop and tablet processors is changing. Laptops are already there thanks to the introduction by Intel of its FinFET-based 22nm process technology several years ago. The FinFET has two key advantages over previous planar CMOS transistors. It leaks up to 10 times less current. Leakage has been in recent years a key source of power loss in processors with more than a billion transistors because all the time any transistors are powered, they leak current even when doing nothing.

The FinFET is also able to switch at higher speeds for a given supply voltage, making the transistor more energy efficient and it is a technology that is now coming to tablets and ARM-based convertibles, which should help their performance as well as battery life.

3) Watching the watts

Although FinFETs increase the performance-power ratio of laptop processors, particularly when it comes to reducing leakage, today’s designs work hard to ensure that precious power is not expended uselessly. Operating systems now watch the activity of applications such as browsers and can disable Flash animations after a while to save on compute cycles.

At the hardware level, it is only when running at full speed that all of the processor cores in one of today’s multicore processors are put into action. The rest of the time, cores can be switched off so they do not contribute to leakage.

4) Voltage co-operation

Processors inside laptops are capable of shifting gears to run at higher clock speeds to handle intensive workloads before shifting back into a more energy-efficient but slower mode. Key to making the most of these gears shifts is the ability to tune the supply voltage at the same. The lower the voltage supplied to a transistor, the less power it consumes. But if the voltage is not high enough, the circuit will not function properly. So, there is a fine balance to be struck.

PC processor cores communicate their needs to power-management integrated circuits (PMIC) constantly. The PMIC responds by providing the processor core with